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Convert NP203 in 1976 D100 to part time 4WD

P

Picaroon

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New Boston NH
My 76 Power Wagon (I know, it's too young to be a REAL Power Wagon) has a decided driveline clunk on the road in 4 high. When it's shifted into 4 high lock on a gravel road or when it's slick on the asphalt, the clunk goes away. I'm hoping this means that the slop is in the power divider and if I install a conversion kit the clunk will be gone permanently. I intend to install lock hubs when I do the conversion (if I remember correctly, the Warn 9790s will bolt up). Has anyone out there got any suggestions as to where I can buy the differential lockout kit? MileMarker used to make them, but I can't seem to find a listing on their website. The truck has a 318 and manual four speed. Any help would be greatly appreciated.
 
I just answered your question in the welcome thread about swaps . As far as this clunk your getting ? We would need more info like "when is it doing it ?" . While your driving ? When you first put it in gear ? Only on turns ? Is it coming from the front or rear or maybe under you ? Things like that . It could be as simple as a joint or it might even be the chain in your 203 T case that's been stretched and will need to be changed . ... As far as the T case conversion kit . I can check with my suppliers to see if I can get you one if you end up going that rout . But honestly , that wont fix your clunk .
 
Bear, first off, you're right - it's W, not D. And thanks a lot for the info about other choices to convert.

The clunk happens on the road when I get on and off the fuel, and when I shift. If I do it calmly and softly, the slack is hardly noticeable, but it's there. When it first started, I pulled it over the pit and checked the driveline, my first thought being that I had a U-joint on its way out. The driveshaft and axle joints are all tight.

The background on this truck- It was owned by an old friend and run by him and others. Rode hard and put away wet. He had parked the thing, his health got worse and it sat in a shed for five years before he died. His heirs were going to scrap it and that's when I took it over. It needed surprisingly little to get it on the road. I did the front end - brakes, left axle, bearings and springs. That was five years ago. When I started it had 52k on it and it's got about 62 now. I run it around local in the good weather and my brother in law plows his driveway with it in the winter - very slowly and carefully. I can walk faster than he plows.

When I got it it had good rubber (ASR) rubber on it, but there were two distinctly different sets front and rear. I ran this for the first couple of years and then put a set of new lug tires on it, all the same size. I think that running the odd size tires probably accelerated the transfer case wear, but I didn't notice the clunk until afer I put the new rubber on it.

When I pull the unit into high lock (NOT on a dry hard road) the clunk either dissappears completely or becomes so faint I can't feel it. This is why I thought the slack might be in the differential, because if it was in the chain, you'd think it would be noticeable whether it was locked in or not.

I think the best and cheapest way out of this would be to convert the NP203 to part time. This truck is never going to do much more than it's doing now - no long hauls or long heavy tows - so for the price of the kit and a pair of Warn hubs (I think someone told me that the 9790s fit this) it could be made to work. I have a well equipped shop at my disposal - pit, overhead cranes, welders, press, all the tools - so all I need is the ambition and a word or two of advice from you guys. Or I guess I could just shift real smoothly, use an easy throttle foot and hope for the best. I've worked my way into my eighth decade, so the truck will probably outlast me whatever I do.

Thanks again for the quick comeback. This is a great forum.

Mark
 
First off, welcome to the site. Second, I would never recommend putting different size tires on a four wheel drive. I'd put money on that being the beginning to your clunk. It's making your diffs run at different speeds from each other creating a whole lot of strain on your driveline. Bear's right with a possible stretched chain in the TC. I'd also check the play in the front and rear pinions. The part time kits can be found on eBay. Being that it's a half ton you won't be able to just bolt on manual hubs. You need the outer axle stubs, spindles and wheel hubs with the internals from a manual hub dana 44. A donor axle is the best bet for this that way you have everything that you need as apposed to shopping for pcs. Hope this helps.
 
Thanks for the tips. The tires were on the truck when I got it, probably should have replaced them earlier. It's begining to look like a full bore overhaul of the TC is in order, and maybe a junk yard scrounge for a Dana 44. Does that have to be from a Dodge? Strikes me that the early 80s Fords and Chevys used them too.

I think the problem is all in the TC. When I first checked it, I jacked it fore and aft and checked differential play. There was little if any. I'm going to check again, though.
 
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You're better off sticking with dodge, then you know everything will swap. Yes chevy and ford used them. I don't know what the spring center is on the ford but the parts won't interchange. Chevy dana 44 parts will interchange to certain extent and the spring centers are different but not by very much. I've bought a power wagon before that had a 10 bolt in the front. Used parts of that to repair a dodge 44. So there are options out there. I have a link to a guide that tells you all about what interchanges with what. I'll do some digging see if i can find it.
 
I an trying to understand how the NP203 functions. From what I can determine the front axle is driven directly from the chain drive and the rear axle threw the differential at back of transfer case. Would this not act the same as a open drive axle? Would power still flow to the rear axle with the front drive shaft disconnected or will it just sit there and spin the front yoke?
 
If you do end up swapping axles then make sure you get an axle out of a pre 79 Dodge truck . The wheel bolt patterns changed in 80 from 5 on 4 1/2" to 5 on 5 1/2" . Unless you want to swap to the large bolt pattern . Then swap out the front and the rear , so they will match . If you do that then look for a Dodge from 80 to 93 . That swap would also give you your part time axles . What would be ideal ( If you did that ) would be axles from an 80 to 85 because there would be no CAD system and it would have factory locking hubs ........ Oh yah one more thing . Someone mentioned that they don't make a hub kit for the early full time four axles . In fact they do . But there made out of plastic and there not very strong . I personally don't like them . I'd rather swap to a later axle myself . Like I did with Big Red . Just my two cents .
 
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